Prior co-pending applications Ser. No. 06/565,540, filed Dec. 27, 1983, and Ser. No. 06/589,640 filed Mar. 14, 1984, both assigned to the assignee herein, disclose a viscous product dispenser utilizing a free-floating take-up piston which automatically responds to the discharge of a volume of product from the dispenser by moving under the influence of atmospheric pressure to "take up" the space in the chamber left vacant by the discharged product. It has been found that in isolated circumstances during shipment or other handling of the dispenser, a sharp blow to the dispenser may result in the take-up piston inching forwardly in the product chamber by a small increment, notwithstanding the fact that the actuating lever has not been depressed. Because the take-up piston is provided with one-way retaining structure which prevents it from moving in a reverse direction, once the takeup piston has been jarred forwardly, it applies an additional loading pressure to the contents and encourages at least a minimal amount of seepage from the discharge spout of the dispenser. This can occur to a certain extent even though the actuating lever as disclosed in such prior applications is provided with a shutoff valve flap integral therewith that covers the outlet of the spout during periods of nonuse.
Another prior co-pending application Ser. No. 06/653,297, filed Sept. 24, 1984, also assigned to the assignee herein discloses and claims a removable shipping seal in the form of a tape or the like which covers the discharge spout of the dispenser and guards against seepage in that manner. Prior to first actuation of the device, the tape is simply pulled from the spout and discarded.